The present invention relates generally to high temperature furnaces for treating molten materials. More particularly, the invention relates to a high temperature wall construction which is suitable for use as a suspended backwall in a glass melting furnace.
The functioning and charging of a typical glass furnace having a conventional suspended backwall or suspended arch, as it is sometimes referred to, is described more fully in U.S. Pat. Nos. 4,197,109 and 3,868,031, both in the names of John Earl Frazier and Clifford F. Crouse.
The suspended backwall having a refractory brick hot face extends downwardly from the roof at the rearward end of the furnace tank and is spaced inwardly from the fixed rear wall of the molten glass tank. The lower edge of the suspended backwall is spaced above the level of the molten glass. This area of the glass furnace is commonly referred to in the art as the "dog house" and provides an open charging area between the level of the molten glass and the lower edge of the suspended backwall into which a batch mixture of raw glass forming solid ingredients is introduced, usually by known feeder or charger apparatus, such as a blanket charger, screw charger, plunger charger or the like.
Heretofore, the construction and maintenance of suspended backwalls have collectively proven to be quite time consuming and expensive. In addition, costly energy losses due to conductive heat transfer through known suspended backwalls has heretofore been a continuous problem in the operation of glass melting furnaces.
The present invention solves many of the problems found in conventional suspended backwalls by providing an insulated furnace backwall construction which greatly reduces heat losses from the furnace while improving the structural integrity of the wall itself.
The present invention further provides a structure which is suitable for use as a suspended backwall, shadow wall, waist wall or furnace roof having a completely closed and fully bonded hot surface face.
Still further, the present invention provides a suspension system for supporting the refractory face tiles having an equalized loading distribution and which permits vertical and horizontal thermal expansion of the suspended refractory tiles. In addition, the present invention provides vertical structural members for supporting the refractory tiles wherein the vertical members are free to move laterally in response to thermal expansion and contraction in the refractory tiles. This improves the thermal and structural integrity of the wall. The refractory tiles of the invention have specially shaped horizontal faces and side edges to matingly engage adjacent tiles on four confronting surfaces to provide a tight and structurally interlocked refractory construction, which prevents so-called "rat holes" from forming in the wall.
Still further, the suspended wall of the present invention provides for continuous and efficient air flow along an inner, cold face thereof to prevent oxidation and weakening of the cast metal refractory hangers without damaging back pressures, as commonly present in prior systems. The invention also provides emergency natural draft air flow in the event of fan failure in the forced air flow system.
In addition, the present invention provides a suspended backwall for a glass furnace having an angularly disposed nose section which may be of a preselected slope to more efficiently, reflectively direct the radiant heat from the burners to the raw charge located in the so-called fritting chamber of the furnace. The refractory tiles forming the suspended wall in the curved or sloped fritting chamber and at the charging end can be selectively removed and replaced from the cold side of the wall during operation, making maintenance much easier than prior wall designs. Still further, the suspended wall of the present invention can be constructed in a shorter time than prior walls of this type, thus enjoying the benefit of lower labor costs. An additional advantage of the invention is hangers made from a high temperature resistant stainless steel which permits the slots in the refractory tiles which receive the inner ends of the hangers to be located in relatively closer proximity to the hot face edge of the wall than was possible with prior art hangers and thereby increases the support of the tiles and decreases the structural failure of the tiles.